Star wheel sensors are used in square balers to measure the length of the bale being formed to determine when to initiate a knotting cycle. They are also used in pairs as electrodes to measure the moisture content of the crop material, as described in U.S. Pat. No. 6,377,058.
The top of a baling chamber in a square baler is formed by longitudinally extending beams that are separated by slots. The slots receive lengths of twine that pass around the bale, the ends of the twines being knotted together by a knotter once a bale has reached the desired size in order to tie the finished bale.
When mounting a star wheel sensor on top of the baling chamber, the star wheel is commonly positioned so that its teeth pass through one of these slots to make contact with the crop material of the bale in the process of being formed. However, a problem is then encountered is that on occasions twine can become entangled with the teeth of star wheel and be wrapped around its axle. This can damage the sensor and interfere with the discharge of the bale.